1. Field of the Invention
The present invention relates to a digital broadcast receiving system, and more particularly, it relates to a program change detecting function thereof.
2. Description of the Background Art
FIG. 22 is a block diagram showing the structure of a receiver of a conventional digital broadcast receiving system, and FIG. 23 is a block diagram showing the structure of a recording/reproducing apparatus of the conventional digital broadcast receiving system. The conventional digital broadcast receiving system shown in FIGS. 22 and 23 is based on a system disclosed in Japanese Patent Application Laid-Open No. 9-247603 (1997). As shown in FIGS. 22 and 23, the digital broadcast receiving system includes a receiver 100 and a recording/reproducing apparatus 2, while a monitor 104 is connected to the receiver 100.
As shown in FIG. 22, the receiver 100 has a receiving/demodulating part 111, a packet filter 112, a controller 123, an information table extractor 114, a program selection/acquisition information part 115, a system clock generator 116, a changeover switch 117, a demultiplexer 118, a decoder 119, a digital interface 122, an information table rewriter 124 rewriting an information table obtained from the packet filter 112, a discontinuity information generator 125 detecting that a demodulated signal obtained from the receiving/demodulating part 111 is discontinuous and generating discontinuity information and a recording/reproducing information table generator 126 generating a recording/reproducing information table described later.
On the other hand, the recording/reproducing apparatus 2 has a digital interface 131, an information table extractor 132, a system clock generator 133, a deck part 135 and a buffer 136 as shown in FIG. 23, and additionally has a PCR rewriter 137 rewriting a PCR (program clock reference), a discontinuity information rewriter 138 rewriting the discontinuity information, a discontinuity information detector 139 detecting the discontinuity information, a controller 140 and a display 141 displaying its operating state.
When receiving a digital television signal from the digital interface 131, the recording/reproducing apparatus 2 extracts the recording/reproducing information table by the information table extractor 132. The controller 140 extracts a plurality of information related to programs from the extracted recording/reproducing information table.
The system clock generator 133 generates a system clock 27 MHz of the recording/reproducing apparatus 2 with reference to a PCR included in a transport packet of MPEG2. The discontinuity information detector 139 monitors whether or not an information table of the digital television signal includes discontinuity information, for immediately posting the information table extractor 132, the system clock generator 133 and the controller 140 when the information table includes discontinuity information and reloading the PCR, PAT and a PMT (program map table) thereby minimizing failure resulting from clock discontinuity.
The controller 140 sets a recording bit rate of the recording/reproducing apparatus 2 from information in the information table, performs operations such as error correction and modulation by the deck part 35 and records the recording bit rate in a recording medium.
When the information table includes no information related to bit rate extraction and the recording bit rate cannot be set, the controller 140 sets a mode to a maximum recording bit rate of the recording/reproducing apparatus 2 and records the same. At this time, the controller 140 monitors an occupied quantity of the buffer 136 for posting a user when the rate of a received signal is greater than the recording rate and overflows the buffer 136.
In reproduction, the recording/reproducing apparatus 2 demodulates a reproduced signal from the recording medium by the deck part 135, performs an operation such as error correction and outputs the signal to the digital interface 131. When changing an operation mode from general reproduction to high-speed reproduction or performing rewinding or slow reproduction, the PCR rewriter 137 rewrites the PCR to a correct value while the discontinuity information rewriter 138 adds information indicating discontinuity to the recording/reproducing information table.
The conventional digital broadcast receiving system having the aforementioned structure stores information necessary for recording/reproduction in the recording/reproducing information table as to a program for recording a digital television signal. The information necessary for recording/reproduction includes information indicating the bit rate of the program of the recorded digital broadcast signal, the broadcast starting date, the time length of the broadcast, the title of the program, the broadcasting channel and the type of each stream of the digital broadcast signal. Such an information table is multiplexed on the digital television signal in a predetermined table form, thereby simplifying extraction and acquisition of information in subsequent processing.
In the aforementioned conventional digital broadcast receiving system, system construction of the receiver is disadvantageously complicated since a large number of types of information must be rewritten for changing the program. When detecting program change depending on change of a version number of the information table, it is impossible to cope with such a case that no special order is observed in version numbers of the information table.